Part 4 (1/2)

Characteristics of Helium

Helium, on account of its chemical inactivity and physical properties, is cla.s.sed along with argon, neon, krypton, and xenon in the zero group of the Periodic System, and forms with them the monatomic, inert gases. In this cla.s.s are now placed also the three radio-active gases, emanating respectively from radium, thorium, and actinium. These are generally known as radium emanation, thorium emanation, and actinium emanation. The first mentioned was once called niton. Emanium was the name originally proposed by Giesel for the body now known as actinium.

The calculated rate of production of helium in the series in equilibrium with one gram of radium is 158 cubic millimeters per year.

This corresponds quite well with the experimental results.

Table of Constants

Some of the more important atomic and radio-active constants are given in the following table. They are recorded here to show how helpful the study of radio-activity has been in working out the composition of matter, and to give some idea of the magnitude of the numbers and the minuteness of the quant.i.ties dealt with.

Electric charge carried by each H atom in electrolysis 4.65 10^{-10} e.s.[1]

Electric charge carried by each [alpha]

particle 9.3 10^{-10} e.s.

Number of atoms in 1 gram of H 6.2 10^{23} Ma.s.s of 1 atom of H 1.6 10^{-24} gram Number of molecules per cc. of any gas at standard pressure and temperature 2.72 10^{19} Number of [alpha] particles expelled per second per gram of radium itself 3.6 10^{10} Number of [alpha] particles expelled per second per gram of radium in equilibrium with its products 14.3 10^{10}

[1] The expression 10^{-10} means multiplying by .000,000,000,1; 10^{10} means multiplying by 10,000,000,000.

CHAPTER V

THE STRUCTURE OF THE ATOM

Properties of Radium

A study of the properties of radium will aid in throwing light upon the question as to the building up of the atom. First to be considered are the usual properties which distinguish an elementary body.

Metallic radium has been prepared by a method similar to that used in the preparation of barium. It is a pure white metal, melting at 700, and far more volatile than barium. It rapidly alters on exposure to the air, probably forming a nitride. It energetically decomposes water and the product dissolves in the water. Its atomic weight is 226.

Radium forms a series of salts a.n.a.logous in appearance and chemical action to those of barium. In the course of time they become colored, especially if mixed barium salts. The radiations from radium produce marked chemical effects in a number of substances. Carbon dioxide is changed into carbon, oxygen, and carbon monoxide, and the latter is changed into carbon and oxygen. Ammonia is dissociated into nitrogen and hydrogen; hydrochloric acid into chlorine and hydrogen. Oxygen is condensed into ozone. In general, the action upon gases appears to be similar to that of the silent electric discharge. Water is decomposed into hydrogen and oxygen. If moist radium chloride or a salt of radium containing water of crystallization is sealed in a gla.s.s tube, the gradual acc.u.mulation of hydrogen and oxygen will burst the tube.

The radiations rapidly decompose organic matter with the evolution of gases. Thus grease from stopc.o.c.ks of apparatus used with radium or paraffin will give off carbon dioxide. Under an intense alpha radiation paraffin or vaseline become hard and infusible. White phosphorus is changed into red.

The action upon living tissue is most noteworthy, as its possible use as a remedial agent is dependent upon this. A small amount of a radium salt enclosed in a gla.s.s tube will cause a serious burn on flesh exposed to it. It therefore has to be handled with care and undue exposure to the radiations must be avoided. Cancer sacs shrivel up and practically disappear under its action. Whether the destruction of whatever causes the cancer is complete is at least open to serious doubt.

The coagulating effect upon globulin is interesting. When two solutions of globulin from ox serum are taken and acetic acid added to one while ammonia is added to the other, the opalescence in drops of the former is rapidly diminished on exposure to radium, showing a more complete solution, whereas the latter solution rapidly turns to a jelly and becomes opaque, indicating a greatly decreased solubility.

Energy Evolved by Radium

The greater part of the tremendous energy evolved by radium is due to the emission of the alpha particles, and in comparison the beta and gamma rays together supply only a small fraction. This energy may be measured as heat. It was first observed that a radium compound maintained a temperature several degrees higher than that of the air around it. The rate of heat production was later measured by means of an ice calorimeter and also by noting the strength of the current required to raise a comparison tube of barium salt to the same temperature. Both methods showed that the heat produced was at the rate of about 135 gram calories per hour. As the emission is continuous, one gram of radium would therefore emit about 1,180,000 gram calories in the course of a year. At the end of 2000 years it would still emit 590,000 gram calories per year. Such a production of energy so far surpa.s.ses all experience that it becomes almost inconceivable. It is futile to speak of it in terms of the heat evolved by the combustion of hydrogen, which is the greatest that can be produced by chemical means.

This effect is unaltered at low temperatures, as has been tested by immersing a tube containing radium in liquid air. It should be stated that these measurements were made after the radium had reached an equilibrium with its products; that is, after waiting at least a month after its preparation. The evolution of heat from radium and the radio-active substances is, in a sense, a secondary effect, as it measures the radiant energy transformed into heat energy by the active matter itself and whatever surrounds it. Let us repeat, therefore, that the total amount of energy pent up in a single atom of radium almost pa.s.ses our powers of conception.

Necessity for a Disintegration Theory